When a beatmap is first made, it is in the Pending or Work in Progress sections of the forum. These maps are referred to as "unranked". Unranked maps do not have a scoreboard and go to the Graveyard section of the forum after a period of inactivity. In order for a map to have a scoreboard and to be moved to the "Ranked" section of the forums, a map must go through the beatmap approval process. First it must get bubbled, and then ranked. Only BNs can bubble and subsequently rank a beatmap.
Before a beatmap can become ranked by a BN (Beatmap Nominator), it must first get bubbled. In order for a beatmap to become bubbled, it must follow and be in accordance with the ranking criteria, and it must have at least 12 Star Priority (or SP). You can actively gain SP in two different ways. First, you can have others help mod your map. If you find their mod to be useful and give kudosu, you will gain 1 SP. You and/or others can also spend kudosu in order to "star" your map (A star costs 1 kudosu, and can be done through either the mapper's profile or through the map's thread). Once a beatmap has at least 12 SP, a BN can bubble it if they feel it meets two conditions:
Mode-Specific Bubbles are bubbles applied to hybrid mapsets for specific modes. The criteria for any of these bubbles is regulated to its respective Ranking Criteria, however only Mode-Specific BNs can apply these bubbles. For a list of available BNs, see the respective list on its article.
Updating a Bubbled beatmap will cause this icon to replace it, it means it needs to get into bubbled status again, alternatively a BN that disagrees with the judgment of the other staff member may place this icon as well. Some BNs place this icon on your map while modding it to prevent another BN to look at it, and is very likely it will get ranked afterwards.
Note: If your map has a bubble, then it will be popped if you update it. If the update was not drastic (e.g. All you did was fix a slider), then just ask the BN who bubbled it to rebubble it. Your map will gain 5 SP for a popped bubble icon.
Once a map is bubbled, a BN can qualify it if the map meets the two criteria listed above. The reason two approval team members are required to check a map is because human beings make mistakes, and this greatly reduces the times of that a map makes it through the ranking system with a drastic error. If a map gets qualified but approval team members or anyone else found it missed a drastic error (e.g. A 5mb video is included in the
.osz that is not used), then it might get disqualified. After a map got into the qualified section for a certain amount of time (usually about one week) with no errors been found, it will automatically get ranked afterwards.
People make mistakes. Therefore, if a map makes it through the approval system with a drastic error, then it might become temporarily disqualified. If your map gets disqualified, you need to address the unrankable issues in order to fix what was wrong, so that your map may become re-qualified and be enjoyed as quickly as possible.
Note: You'll sometimes be asked to change things you do not want to change. Sometimes you may be able to get away without changing it, but if half the Beatmap Nomination Group agree that you should change it, then let go of your pride and just fix it.
Following up from ranked, a BN can approve these beatmaps if they are longer than 5 minutes long (aka marathon beatmaps) and/or that do not follow the ranking criteria but are considered "okay" by a BN.
Note: Beatmaps (that are less than 5 minutes) are planned to be ranked, not approved!