complex and compound sentences

[ere73]

Would you tell me what are the differences between complex sentences and compound sentences, please

[irinka]

Hi!
It's a difficult question since the terms are not frequently used nowadays. Anyway, a compound sentence consists of co-ordinated (of the equal status) simple clauses, such as in The weather was fine and the children went for a walk.
a complex sentence consists of a matrix clause (the superordinate) and one or more embedded (subordinate) clauses (as you see they are not of equal status), such as in I want [to know] [when it all happened] (the bracketed elements are subordinate clauses).
However, I would recommend to use the more recent terms, such as matrix and embedded (subordinate) clauses. By matrix clause we mean the sentence as a whole (the superordinate) and by the embedded clause we mean the dependent clauses. In the example: I want [you to do it for me], the whole sentence represents the matrix clause, whereas the part "you to do it for me" is a nonfinite (no tense features) subordinate clause, represented by a small (verbless) clause.
take care, Irinka