I was a student teacher ....

What is the meaning of TA and the difference from student teacher then ?

Here in the us a student teacher is a person who is in college and working towards becoming a teacher. The ST will go into the classroom with an experienced teacher who will fill out performance rating forms and the student teacher gains experience from the process.

Ooh

I was just coming to that class to help out (out of interest) when i was younger than the students i was helping, but the electronics teachers adopted me as assistant

Now that i am in college i come there too to do the same (this time as part of community aid program of the college - i report the hours i do helping in class to the college), but its not much to do with my actual studies there (some other students in the electrical engineering help kids in schools with unrelated subjects, some others do totally different stuff like "green projects" under the same community aid program)

Teaching Assistant or Teacher's Assistant depending on various vernacular minutiae.