"Sonata form" normally applies to the first movement of a symphony or sonata.
Basically:
EXPOSITION: consisting of FIRST SUBJECT in the principal key, a bridge to the SECOND SUBJECT in a related, e.g. dominant, key, and possibly a CODA,
DEVELOPMENT or working out (i.e. variations, meanderings etc on the first and second subjects,
RECAPITULATION of the first two subjects.
These are formal rules as used by C.P.E Bach and Haydn. Practically every composer since then has broken these rules.
"Rondo-Sonata Form" is similar, except that the first subject is repeated after the second, and there may be a third subject as well. A Rondo is a round, or canon.
As composer, of course you're free to construct your piece any way you like. I think a degree of formality lends coherence. The same applies to songs - many, if not most, older Broadway songs are very tightly constructed indeed - the lyrics as much as the melody. Listen to Cole Porter (and enjoy!).
Best of luck with your composition.
Sarah