Both the renewal and the extension of a contract results in the prolongation of the lease term in everyday terms.
Generally speaking, renewal refers to the situation when a contract for a definite term becomes prolonged with another term, usually with the same duration as the original term.
In case of extension, the contract is prolonged to a certain date. IN this case the contract will expire at the date specified in the extension clase.
Let's look at a practical example.
If a contract commencing on January 1 and expiring on December 31 is renewed, it is like to remain in effect for another term of one year, that is the final expiration will be one year later.
If the same contract is extended, it may end at a certain date to be specified by the parties, e.g. it may be extended by the end of May.
However, please note that the terms standing alone do not always carry this meaning. When we use a heading in a contract regulating various ways to prolong the expiration, both renewal and extension are used nearly interchangeably.