Whats the difference between keppra and lamotrigine

I had 3 grand mahl seizures about a year and a half ago. I was diagnosed with epilepsy and put on keppra, but was raised to 100mg of lamotrigine a few months later. I dont know the significance of dose sizes or types of medication. Is it a heavier dose or pretty light. I do drink every other weekend and do smoke weed have'nt had any problems, i know everyones is different but just curious as im pretty new to this and never really consulted anyone on it.