explain vs tell
Explain:
To make something clear or easy to understand by describing or giving information about it.
If there's anything you don't understand, I'll be happy to explain.
The teacher explained the rules to the children.
[+ question word] Our guide explained where the cathedral was.
He explained how the machine worked.
Please could you explain why you're so late.
[+ that ] She explained that she was going to stay with her sister.
[+ speech] "Someone must have hit the wrong button," an official explained.
[R] Molly asked the teacher if she could explain herself a bit more clearly (= say more clearly what she meant).
No one has been able to explain (= give the reason for) the accident.
Tell (SPEAK):
To say something to someone, often giving them information or instructions.
Tell me about your holiday then.
[+ two objects] Can you tell me the way to the station?
[+ object + (that)] Did you tell anyone (that) you were coming to see me?
[+ object + speech] "I'm leaving you," she told him.
[+ object + to infinitive] I told her to go home.
Formal He told us of his extraordinary childhood.