What does the ( ' > ) symbol mean in the command line in MySQL?
It means that it is treating any input which follows as part of a string literal, until it encounters a(n unescaped) string termination quote ' character.
This will have happened because you previously began the string literal with such a string termination quote character. For example:
mysql> SELECT foo -> FROM tbl -> WHERE bar LIKE 'somestring '> this is still part of somestring' -> ;
It means you have an incomplete query. Most likely it's something related to a missing quotation, semi-colon at the end, or parentheses aren't closed.
You can exit the query with: '\cNot sure what happens to the query but it gets you back to the mysql> prompt.