Simple interest is interest paid on the original principle only, Compound interest is the interest earned not only on the original principal, but also on all interests earned previously.
Hobby is something people does for pleasure or because they feel like it. Interest are something people are interested in which is very similar to hobbies.
well, its the stuff dat u really like 2 do and it entertains you, that what a hobby is and an interest is like something dat u want 2 learn more a bout.