user116237: I know I can't send coin without my passphrase, but I have forgotten it. All I would like to know is, is the passphrase a phrase I come up with? Or does Bitcoin Core provide the phrase? Many thanks.
Also is it just one word or a sequence of words?

user13866: 
is the passphrase a phrase I come up with?

Yes.
It is used to encrypt the wallet so that only you can use it.

is it just one word or a sequence of words?

It is up to you what characters to type and whether it includes spaces.
The program suggests "Please use a passphrase of ten or more random characters, or eight or more words"  So, if you are the sort of person to heed advice, you probably chose a passphrase following one or the other of those forms.

I have forgotten it.

See Are there Bitcoin password crackers I can use to recover forgotten passwords?
Don't use any online tools.

116237: <p>I know I can't send coin without my passphrase, but I have forgotten it. All I would like to know is, is the passphrase a phrase I come up with? Or does Bitcoin Core provide the phrase? Many thanks.</p>
<p>Also is it just one word or a sequence of words?</p>
 13866: <blockquote>
<p><strong>is the passphrase a phrase I come up with?</strong></p>
</blockquote>
<p>Yes.</p>
<p>It is used to encrypt the wallet so that only you can use it.</p>
<blockquote>
<p><strong>is it just one word or a sequence of words?</strong></p>
</blockquote>
<p>It is up to you what characters to type and whether it includes spaces.</p>
<p>The program suggests <em>&quot;Please use a passphrase of <strong>ten or more random characters</strong>, or <strong>eight or more words</strong>&quot;</em>  So, if you are the sort of person to heed advice, you probably chose a passphrase following one or the other of those forms.</p>
<blockquote>
<p><strong>I have forgotten it.</strong></p>
</blockquote>
<p>See <a href="https://bitcoin.stackexchange.com/q/3313/13866">Are there Bitcoin password crackers I can use to recover forgotten passwords?</a></p>
<p>Don't use any online tools.</p>
