Variation Margin vs Maint. Margin in futures markets

Ok: I always screw this up. In futures markets, I have to be above the maitenance margin right? What is the variation margin? Is that the amount to be paid in? (I thoguht you have to pay up the the initial margin?)

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Initial margin is paid upfront to make trade, variation margin has to be deposited to bring balance to intial margin after receiving margin call (balance falls bellow maint. margin) dont confuse with equity investments, where after margin call balance has to be increased to maint. margin not intial margin in equity inv. maring acts as a loan and there is interets charges, in futures it’s not a loan. also in equity margin is determined by Fed and can be further reduced by broker for futures margin is set by clearing house