When he sends you memes it means he wants you to smile and he has a level of familiarity with you. Guys send memes as a way of being friendly or even more than friendly with someone, and it also means that they know what appeals to your funny bone, which is why they are able to send you GIFs or memes that make you laugh. Some people also send memes when they want to stay in touch and keep the connection alive and may not have something to say, necessarily, so they send funny jokes and memes that they know will entertain you in some way.