Sorry for the long answers
Content ID matches are when a rightsholder uploads a reference clip to YouTube. This can be audio-only, video-only, or audiovisual (both, obviously). It was created to:
a) please content owners and dissuade them from sending DMCA notices by offering to manager their content on YouTube, and
b) allow content creators to use and/or sample content without the fear of an immediate takedown.
If a video is identified as a content match, the owner can block, monetize, or track the statistic. Most often, the rightsholders monetize their content since it makes them money. Of course, full-length TV shows and movies are blocked since the ad revenue generates less much than a $2 rental on-site.
While it is not an explicit license or permission per se
, one could interpret that a claim that is identified but not blocked by the system means that the rightsholder is tolerating the use of his or her property in exchange for the ad revenue. DMCA claims for Content ID matches are rare, unless it is a part of the appeals process which it is the only option besides releasing the claim.
A "Content ID strike", as they are informally called, is when a video is blocked worldwide on YouTube. This is also rare, but it happens most often when people upload things like TV shows, movies, and music videos. When a video is blocked worldwide via Content ID, it makes your account not in good standing and takes away some of your features. It is basically a DMCA strike with a lot less formality, but the same amount of impact. Your account can be returned to good standing by either appealing the claim or deleting the video.
While an account with community and copyright guidelines in a good standing but not Content ID will probably not be accepted for a partnership, a simple Content ID match (i.e: a monetize one) most likely will not be an issue. These just lessen the amount of videos on your channel that your network can claim, so if you have a collection of videos all with Content ID claims on them, the network can't make money since you
can't make money.
In other words, one content ID claim is not going to kill your account. However, some networks have a no-tolerance policy to things like third-party music and you should be aware if that's the issue.