Translation:An apple and a pen
You use -와 after vowels and -과 after consonants. So for example: 아이와 “a child and…/with a child” but 어른과 “a grown-up and…/with a grown-up”.
There are other particles which basically mean the same thing, namely -(이)랑 (add the -이- after a consonant) and -하고. Both of these sound rather colloquial though. In situations with any semblance of formality I would stick to -과/와.
Also note that all the above particles only combine with nouns. With verbs you have to use different particles. -고 is the closest equivalent but there are others which can in the right situation correspond to English “and”.