The difference is how the past tense of the verb is formed.
For regular verbs all past forms end in -ed:
walk -- walked, talk -- talked, listen -- listened etc
For irregular verbs the past tense may be the same word:
cut -- cut, hurt -- hurt
or it may be a different word:
run -- ran, eat -- ate, do -- did, understand -- understood.
"Have" is an irregular verb in English.
"Wrote" is an irregular verb.
Shown is an irregular verb because shown is different to ending in -ed. Does shown end in -ed? No it doesn't end in -ed so which makes it an irregular verb.
No, "appeler" is a regular -er verb in French. It conjugates according to regular -er verb patterns.
"Fly" is an irregular verb. Its past tense is "flew" and its past participle is "flown."
"Have" is an irregular verb in English.
regular or irregular
"Wrote" is an irregular verb.
It's an irregular verb.
It's an irregular verb.
To swim is an irregular verb.
Ate is an irregular verb.
It's an irregular verb.
It's an irregular verb.
irregular
irregular
By is not a verb, so it is neither regular nor irregular.