Yes, I can. If the word 'them' refers to the people who need the explanation (indirect object - dative case), then it has to be 'explain to them'. For example: 'I'll call the passengers and explain to them what the situation is'. You cannot say 'explain them' in this situation. This is a very common mistake, even among advanced learners. The only way that you can use 'explain them' is if the pronoun 'them' is the direct object of the verb (accusative case) ie the thing which is being explained to the people. For example: 'The instructions were difficult so I asked my teacher to explain them to me.' I hope that helps.

When we say "explain X", then X is the mystery. If there's a listener, then we say "explain X to (somebody)". We can't use the "[verb] [indirect object] [direct object]" pattern simply because the verb "explain" doesn't work like that. There are a few other verbs which cannot take this pattern, although the common learner mistake is to assume this word order is automatic. On top of that, the English pronoun is the same for both direct (accusative) and indirect (dative) objects. So, a preposition is needed here to show who the listener is. When a student writes "please explain me...", then to native speakers, "me" is the mystery and it sounds funny that the writer is completely confused by him/herself! :)