Splinterlands guilds are groups of players battling under the same name. These different rank levels will provide you with different abilities within the guild.
Member: This is the lowest level of the guild and has the fewest abilities to make changes within the guild. You can talk in the tavern and challenge other guild members to battles. You can also contribute DEC to buildings and your daily focuses go toward the lodge's progress.
Sr. Member: As a Sr. member you will be able to do everything a member can but you can also promote other members to Sr. Member. You will also gain the ability to remove people from the guild that are below your rank (which are Members).
Officer: As an officer, you will retain the abilities of Member and Senior Member. You can also promote people to officers and kick anyone who is a Member or Sr. Member. Along with this you can accept and invite people into the guild as new members, as well as assign people to the Frays or boot them from a Fray before the Guild Brawl starts. Also, you are able to move the brawl tiers up and down depending on the level of the Arena to get better rewards from more brawls, but only during the result phase.
Co-Leader: As Co-leader you have all the abilities of the lower ranks. In addition to this, you can edit the guild announcement and spend the crowns earned by the guild to upgrade the buildings and buy Spy Glasses. You can also promote other members up to your rank of Co-Leader.
Leader: As the Leader, you can do all the previous functions of the lower ranks, as well as kick and promote anyone in the guild. Along with this, you can also transfer the ownership of the Guildhall to a new Guild Leader.