user109: The question basically says it all, but I'll try to elaborate a bit:
Are there differences in terms of the concepts used in each of these branches?
Are there differences in the practices of each of the branches?
Or are the differences between each of the branches simply explained in terms of historical or geographical factors?

user43: As @bytebuster said, this could take an expert a book to answer. But in the spirit of constructive collaboration, let me throw in my two cents:
In Theravada, the focus is on escaping from Samsara to Nirvana, mainly through attaining perfect control of your mind, which in day-to-day life manifests as practice of minimalism.
In Mahayana, the focus is on transcending the dichotomy of Nirvana/Samsara, and realizing the Buddha Nature, mainly through deconstructing the ego; in day-to-day life this manifests as practice of altruism and non-attachment.
In Vajrayana, the focus is on liberating the mind from mental and emotional obscurations so that it can fully enjoy the Natural Perfection that does not need to be attained.

user4: This question, indeed, requires a whole book in order to be answered completely. Let me address only Theravada and Mahayana here.
In two words:

The most important aspect is that Theravada is focused on your own liberation from suffering, while Mahayana is targeted to all sentient creatures;
There are many consequences here:

Theravada assumes that you have to practice for yourself, while others can only suggest you. Mahayana says that you can (and have to) share your experience and accomplishments with others, thus making followers for yourself;
Theravada suggests to seek enlightenment for yourself first; Mahayana is up to delaying breaking off Samsara in order to help others;
Theravada practices are mostly silent and very personal while in Mahayana it is more often "wrapped" in some collective rituals like chanting;

In Theravada, the final goal for a Bodhisattva is nirvana. In Mahayana, prominence is important by itself;
Each teaching is more or less localized, e.g. at a certain country/territory there's usually only one;
If you'd like to read scriptures in original language, you should be aware that Theravada is written in Pali (Pali Cannon) while Mahayana is written in Sanskrit (Sutras);

Of course, there are also big differences in texts, ritual, etiquette, and so on.
This Comparative Study between two traditions provide with greater details.

109: <p>The question basically says it all, but I'll try to elaborate a bit:</p>

<p>Are there differences in terms of the concepts used in each of these branches?<br>
Are there differences in the practices of each of the branches?<br>
Or are the differences between each of the branches simply explained in terms of historical or geographical factors?</p>
 43: <p>As @bytebuster said, this could take an expert a book to answer. But in the spirit of constructive collaboration, let me throw in my two cents:</p>

<p>In Theravada, the focus is on escaping from Samsara to Nirvana, mainly through attaining perfect control of your mind, which in day-to-day life manifests as practice of minimalism.</p>

<p>In Mahayana, the focus is on transcending the dichotomy of Nirvana/Samsara, and realizing the Buddha Nature, mainly through deconstructing the ego; in day-to-day life this manifests as practice of altruism and non-attachment.</p>

<p>In Vajrayana, the focus is on liberating the mind from mental and emotional obscurations so that it can fully enjoy the Natural Perfection that does not need to be attained.</p>
 4: <p>This question, indeed, requires a whole book in order to be answered completely. Let me address only Theravada and Mahayana here.</p>

<p>In two words:</p>

<ul>
<li><strong>The most important aspect</strong> is that Theravada is focused on your <em>own</em> liberation from suffering, while Mahayana is targeted to <em>all sentient creatures</em>;<br>
There are many consequences here:
<ul>
<li>Theravada assumes that you have to practice <em>for yourself, while others can only suggest you</em>. Mahayana says that you can (and have to) <em>share your experience</em> and accomplishments with others, thus making followers for yourself;</li>
<li>Theravada suggests to seek enlightenment <em>for yourself first</em>; Mahayana is up to <em>delaying breaking off Samsara</em> in order to help others;</li>
<li>Theravada practices are mostly silent and very personal while in Mahayana it is more often "wrapped" in some <em>collective</em> rituals like chanting;</li>
</ul></li>
<li>In Theravada, the final goal for a Bodhisattva is nirvana. In Mahayana, prominence is important by itself;</li>
<li>Each teaching is more or less localized, e.g. at a certain country/territory there's usually only one;</li>
<li>If you'd like to read scriptures in original language, you should be aware that Theravada is written in Pali (Pali Cannon) while Mahayana is written in Sanskrit (Sutras);</li>
</ul>

<p>Of course, there are also big differences in texts, ritual, etiquette, and so on.</p>

<p><a href="http://buddhanet.net/e-learning/history/comparative.htm" rel="noreferrer">This Comparative Study</a> between two traditions provide with greater details.</p>
