Meanings of the stretch are "to lengthen", "widen", "to extend" in dictionary.
Stretch also can be defined to lengthen and to relax the muscles on the
body.
Basically, anyone sees the yoga asana think of expand and the relax the muscles first.
Therefore, they might regard yoga as just a stretch but there's more to
yoga than stretching even if it is important to lengthen and relax.
Difference of benefit between yoga and stretch
Stretching before or after workout can prevent from a sports injury.
Practicing yoga asana improves a balance and recover the body.
---------------------------------------
Ask
Q: Do I have to endure such pain while I'm stretching ?
A : You should do stretching little by little to avoid the risk of injuries
even though you are inevitable that you have to endure the pain to
be flexible.