This is a great video about textures all of them you can see the diffrence in the video and thanks Grant Abbitt for this video 
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Video
this is how u can hand paint in blender u can make some great looking textures not using photoshop or something else
Exemple Base color texture (made by CGArt VN
Artist) : this is an base color texture it’s an 2d texture
But if u create an Normal Map for this texture it will make look like 3d and it can help you and the game engine to render less verts and tris if it’s an simple cube like 6 faces u can create a 3d look with this texture base it on normal map
it’s made by : ARTsWIKIPEDIA
and this is how u can create a normal map texture for more 3d realism
and there is a Texture Occlusion map but i don’t know about it so sorry for that for what i’v heard it’s about how rougthness , or pbr texture looking more realistic ! sorry again for my bad english i hope u learnd some thing here Thanks !