Should be renamed to Server, seeing as Spoonhead was just the name that the workers gave them, as a joke.
Talk about it here.
Spoonheads were robots created to help the Great Intelligence. The term "Spoonhead" was coined by Alexei; Miss Kizlet, the leader of the group that used the Spoonheads, referred to them as "servers," and expected the rest of the team to do the same. The Eleventh Doctor described one as a "walking Wi-Fi base station" that "hoover[ed] up people".
Appearance
In their camouflage state, they looked human except for the back of the head, which resembled a glowing spoon and could rotate. They took their appearance from images the subconsciousness of the individual looking at them. Out of camouflage, it was roughly humanoid, but metallic, with a more pronounced spoon-shaped head without any features and had angular limbs. (TV: The Bells of Saint John)
History
Spoonheads were used by Miss Kizlet's company to upload people's souls to the Internet for the Great Intelligence to feed upon. In 2013 London, a Spoonhead disguised as a little girl from the book, Summer Falls, partially uploaded Clara, but the Eleventh Doctor stopped it.
When another Spoonhead, disguised as the Doctor, uploaded Clara successfully, the Doctor hacked into it, and the Spoonhead, still appearing as the Doctor, rode an anti-gravity motorbike up the Shard. The Spoonhead absorbed Miss Kizlet and used her tablet to raise Mahler's obedience when she asked him to download the entire cloud back to their bodies. (TV: The Bells of Saint John)