There is nothing on the wiki about them. How do I build them and what do I do? Is there any maintenance on them?

Training bases are a type of op built after farm level 4 i think. You can only have one of these. They allow you to build troops, for instance on earth, you have a training base in Greenland, then you can build troops at your training base there, so your troops can go into Europe or something. They have half the training space has your colony's training size, i think. And no maintenance, just protect it

Training bases have a capacity of 30, they are useful when ur alliance is on a major war and u have not yet relocated near the hive and u cant because u have a lack of oil because u can help ur alliance by making a training base near them and training troops near them to help them out untip uve got enough oil to relocate. To make a trainig base, make an op near ur alliance hive and ask them to defend it for 24 ticks, after the 24 ticks, click on ur op then select trainig base