People have a lot of interesting answers for that. For some, it's a class they take at the gym when the treadmills are all taken. For others, it's an incredibly intense and rigid way to find and express their spirituality. Some see yoga as a great way to unwind after a hard day and others see yoga as that obnoxious thing that floods their instagram with pose pictures.
Everyone has an idea as to what yoga should or shouldn't be -- and what yogis should or shouldn't do. Yoga can be the butt of many jokes (including jokes about yoga butt) and the source of a lot of scrutiny.
What do I think yoga is? I think yoga is exactly what you make of it and exactly what you need it to be.
My take on yoga? Yoga is not about forcing yourself into advanced poses and looking a certain way while on the mat. It's not about taking yoga selfies or selfies in your yoga clothing. It's not about being able to touch your toes or stand on your head or balance on your arms.
It's not about anything that would not serve you.
To put simply: yoga is a way to find some peace of mind, tools to handle stress, and avenues to curtail anxiety. To put even simply-ier: yoga is a way to find you. No special poses or wardrobe required. No physical or mental prerequisite. Simply come with an open heart and see where it takes you.
It's kind of like Namaste -- finding the version of the meaning that resonates: The light within me honors the light within you. The driving force within me respects the driving force within you. The good within me acknowledges the good within you.