user22280: Im trying to do an expression to my object. I want to make him come out from the side to center. I searched a lot but I didnt find any expression. I can do it with keyframes but I need expression only. 
Please, can someone help me with expression?

user1950: Expressions work by returning a value to the property to which they are applied. So if you apply an expression to the position property and you put in the expression
[1,2]

in the expression editor, it will return the value [1,2] so that will be the position of that layer, i.e x= 1 y=2. Because the values 1 and 2 don't change, it will stay there forever.
If you have an expression on the position where the x value increases over time then the layer will move right. So for example if you put the expression
[time, thisComp.height / 2]

the layer will start at [0, 540] (if the comp is 1080 px high) and move right at the rate of 1 pixel per second. For a HD frame it will reach the right side at around 1:17:20. That might be too slow, but you can use maths to adjust it. For example to make it twenty times as fast you could multiply it by 2, like so:
[time * 20, thisComp.height / 2]

So in the expressions editor you can see the drop-down with the available objects, properties and methods. You can use these along with the pick-whip to build up the expression to do whatever you need.
You might want to start looking at Dan Ebbert's site. I can't quite believe that anyone could spend any time researching expressions and not find this site in the search results.

22280: <p>Im trying to do an expression to my object. I want to make him come out from the side to center. I searched a lot but I didnt find any expression. I can do it with keyframes but I need expression only. 
Please, can someone help me with expression?</p>
 1950: <p>Expressions work by returning a value to the property to which they are applied. So if you apply an expression to the position property and you put in the expression</p>

<pre><code>[1,2]
</code></pre>

<p>in the expression editor, it will return the value [1,2] so that will be the position of that layer, i.e x= 1 y=2. Because the values 1 and 2 don't change, it will stay there forever.</p>

<p>If you have an expression on the position where the x value increases over time then the layer will move right. So for example if you put the expression</p>

<pre><code>[time, thisComp.height / 2]
</code></pre>

<p>the layer will start at [0, 540] (if the comp is 1080 px high) and move right at the rate of 1 pixel per second. For a HD frame it will reach the right side at around 1:17:20. That might be too slow, but you can use maths to adjust it. For example to make it twenty times as fast you could multiply it by 2, like so:</p>

<pre><code>[time * 20, thisComp.height / 2]
</code></pre>

<p>So in the expressions editor you can see the drop-down with the available objects, properties and methods. You can use these along with the pick-whip to build up the expression to do whatever you need.</p>

<p>You might want to start looking at <a href="http://motionscript.com/" rel="nofollow noreferrer">Dan Ebbert's</a> site. I can't quite believe that anyone could spend any time researching expressions and <em>not</em> find this site in the search results.</p>
