Question

Later that day,my friends arrived and we all enjoyed a lovely meal together.They all praised me

接上for my good results.I expained that is why we were having this lovely party.这是个什么句子、意思是什么

Answer 1

先是宾语从句,后是原因状语从句。
I explained后接宾语『that is why we were having this lovely party』,宾语中又有why引导的状语从句。翻译：我解释这就是为什么我们正在举行这个美好的聚会

Answer 2

整个的意思是：之后我的朋友来了，我们一起享用了一顿佳宴，他们都为我的好结果表扬了我（由于不知道意境，所以不知道好结果是什么意思），我解释了这就是我们开这个派对的原因。