Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
This build is a support alistar build. I mostly build him for auras and for supporting your team.
Most of the items are situational: if the enemy has alot of ad get ninja tabi, if they dont have much ap or cc go boots of swiftness or mobility and if your doing really good get sorc shoes or boots of ionia. For the frozen heart if you need more armor and you're not as dependant on mana get randuin's omen instead of frozen heart.
My preference is ghost and flash so that you can flash behind an enemy and push him into your teammates with your w. Ghost is so that you can chase or run away from enemies or to chase an enemy in order to use your e on them. If your summoner level is lower than 12 get ghost + exhaust or ghost + clarity.