Bandha means something like a lock,  a seal. In yoga we use bandha, certain inner alignment principles, to seal and harness (life) energy inward. Contrary to what busy life usually demands of ourselves, where we spend lots of energy outward... 

Bandha in that sense is an energetic alignment which brings about a certain physical form that works with rooting up from the ground instead of passively collapsing into ground.  This aligned focus paves the way to a certain mental and emotional alignment.  

Altogether understanding / exploring how to access to work from within (vs. the search for outside validation) offers a path of more integrity, grace and strength inside and outside the mat. It also offers a whole new perspective of understanding on various layers of being.  (How are you with yourself? What is your relation to food? To sex? ....)

Bandhas! 
A core aspect of our yoga tradition and definitely worthwhile to study at least for one lifetime :))