"Out-of-market" refers to games that are typically only available outside of your local TV market and are not televised in your local market via your local networks, regional sports networks or national networks. MLB Extra Innings gives you access to out-of-market games only, and does not grant access to any games that are typically televised in your local viewing area.
Subscribing to MLB Extra Innings does not give you access to games of your local team.
For example, if you live in Denver, Colorado, MLB Extra Innings will NOT grant you access to Colorado Rockies games because they are in your local broadcast region. However, if you live in Phoenix, Arizona and want to watch the Rockies, MLB Extra Innings will grant you access to all Colorado Rockies games that aren't subject to local blackout.
Blackout restrictions include your local MLB team(s) and all nationally televised games. So as a Rockies fan living in Phoenix, MLB Extra Innings will allow you to watch all Rockies games EXCEPT games that are nationally televised (e.g. games that air on networks like MLB Network, ESPN, FS1, and TBS) and games where the Colorado Rockies play your local team, the Arizona Diamondbacks.
If you are looking to gain access to your local team's games, MLB Extra Innings will not be the best option for you.