Final selections are this Sunday. You get in either by automatic bid or by an at large berth. There are 31 automatic bids. A lot of teams "on the bubble" are affected by the automatic bids. Basically it breaks down like this...
North Carolina is a lock to get an at large berth. They have been in the Top 10 all season long, and been ranked Number 1 for a good portion of the season. They could be eliminated in the first round of the ACC Tournament and still get nothing lower than a 2nd seed (and will probably get a top seed) in the NCAA Tournament. Likewise, Duke, Wake Forest, Clemson, Florida State and Boston College are also considered locks to get an at large berth if they do not win the ACC Tournament.
Maryland is considered on the bubble (and by many to be on the outside of the bubble looking in). It has been said that they would have to do anything from win 2 games in the ACC Tournament all the way up to get to or even win the tournament in order to guarantee a spot in the NCAA Tournament. The odds of them winning the ACC are slim (there is a reason they went 7-9 in the regular conference season and were the 7th seed going into the tournament last night, where they beat NC State 74-69). But it is always a possibility that they could make it to the ACC Finals, lose, and not get a bid. It is also possible that they could win the ACC Tournament and therefore get an automatic bid to the NCAA's.
If Maryland DOES get an at large berth, then the selection committee has deemed them more worthy than others who were considered borderline teams to make the tournament. But if they were otherwise not going to make the tournament but DID win the ACC Tournament and therefore did receive an automatic bid to the tournament, they would wind up bumping out another team that otherwise was considered stronger than them and would have made the tournament over them if they had not received the automatic bid (dang but that was a long sentence). In that scenario, Penn State or New Mexico could be bumped out of the Big Dance (another nickname for the NCAA Tournament).
In other words, 31 teams get invited no matter what else happened in the regular season. Now the vast majority of the time the teams that get invited no matter what are not competing with the borderline teams for one of the other 34 open slots (the "mid major" and minor conferences are usually one, two teams tops for the tournament, since their SoS and their RPI are not enough to put them in the running). But teams from the major conferences (like MD) who have decent SoS and RPI, but not at levels guaranteeing them an at large berth, have to be one of those 31 teams to get that guarantee. And if they buck the trend and beat those schools above them and win one of those automatic bids they probably knock another school out.
And once they get in there, there is no telling what can happen. And THAT is why I am planning on wasting as much of my bosses' time as possible the next month or so (even more so than usual, which is a hard thing to top. But I shall strive to be as unproductive as possible, furtively glancing at my online scoreboard whenever they are not able to see my screen. It is the American way, you know).