The word "rent" can be used as a noun or a verb. For example, "I need to pay my rent" or "My rent will be late this month". When it is used as a noun, it means "an amount that you pay to use something". When you use the word "rent" as a verb, an example sentence would be "I am renting this apartment." So the verb "to rent" would mean "to pay to use something temporarily". "Rental" is used mostly used as an adjective. An example sentence would be "Don't eat in the car. It's a rental." So, you would use the word "rental" to describe something you are renting. You could also say "I really like this rental." In this sense, the word can be used as a noun.

rent 就是房租，rental 可以是任何东西的租金，比如租车，船，月光宝盒什么的。

Typically rent, as a noun, is only really used to describe the regular payment made to a landlord for a property. If you are talking about a car or house (or any other inanimate object), that you are currently paying rent for, it would be a "rental". If it is not currently being rented it is usually described as "up for rent".