What Is Use Of Taking Lasix?

Hi, my husband has been put on tropan 2.5mg,hes diabetic with hypertension,had a CAB in '99,stenth for the right kidney in2007,suffered a urinery infection a month back, had a lot of swelling through out his body,much better now after taking lasix,he is now on lasix 20mg & now on tropan,would like to know what its for?hes 76 years old. thanks,Fernandez Pune.