Parsvakonasana/Side angle is a standing pose that has many benefits:
Strengthens your legs including your inner thighs, gastrocnemius, soleus, quadriceps, tibialis anterior and ankles (your quadriceps, inner thighs and calf muscles should be contracted in this pose)
Stretches your obliques and transverse abdominal muscles
Strengthens the muscles around your shoulder joints/deltoids
Strengthen your arms including your triceps (your triceps are contracted in this pose)
Strengthens your serratus anterior
Strengthens your TFL (Tensor fascia lata)
Stretches your trapezius and erector spinae
Reduces fat around waist and hips
Relieves sciatica nerve and arthritic pains
Increases peristaltic activity and aids elimination (peristaltic is a type of involuntary muscle movement that occurs in your digestive system.)