What is the purpose of this op amp configuration shown?
It's working as a comparator basically. 


  It is a Schmitt trigger. It has a variable reference value, i.e. controlled using the R2 and R1 resistances. At the non-inverting input (using voltage divider arrangement), $$V_+ = \frac{R_1}{R_1 + R_2} * V_{o}$$ and at inverting input, $$ V_- = Vi $$ at the inverting terminal. Now, output can be either \$ +V_s \$ or \$ -V_s \$ depending on whether non-inverting terminal voltage is higher or not respectively. So, the output is \$\beta V_s\$ or \$-\beta V_s \$ where \$ \beta = \frac{R_1}{R_1 + R_2} \$. If first output is in positive saturation and then \$V_i\$ goes above \$\beta V_s\$, then output changes to \$-V_s\$. Similarly, when \$V_i\$ goes below \$-\beta V_s\$, then output changes to \$ +V_s\$. You can find a lot of websites that explain this circuit. Just search for Schmitt trigger.