Share of wallet (or something similar to it) is the term used by credit industry professionals and what it means is how much of your spend a particular credit card company benefits from. For example, I have a couple credit cards in my wallet right now, each one serving a different purpose, and each one of those has a share of my wallet, along with cash, gift cards, etc. Credit card companies want to get in the game, they want to just make it into your wallet because once they get there, they know you’ll use it. Even if the percentage is small, such as my Discover Gas card, which I use only for gasoline purchases; they know that sometimes I might reach for that Discover card if I’m close to a cashback rebate payout or if I just don’t care what card I’m using (for those places that you only ever get 1% cashback).

This is why places offer 0% balance transfers or 0% purchases or free promotional gift cards for you to sign up, they just want to get a piece of the action and get in the game - i.e. get into your wallet (or purse).