What is the definition of irregular verbs?
A verb is regular if its Past Simple form and Past Participle form end with "-ed".
The examples can be:
play - played - played
stay - stayed - stayed
invite - invited - invited
A verb which is NOT regular is called irregular.
be - was/were - been
go - went - gone
think - thought - thought
There is a difference between American English and British English. Some verbs like burn or learn which are irregular in British English are regular in American English.