Is it cheating to look at/talk to others online or in person while in a relationship with someone?

A friend of mine thinks it's ok to look and talk to others if they aren't getting what they need in their current relationship. For him he's been complaining about him doing all the texting and it feels one sided. I think it counts as cheating personally. My reason being your mind/emotions have checked out with your partner and have gone on to look for someone else.