Reserve - to keep something for a particular purpose or time:

I reserve Mondays for tidying my desk and answering letters.

These seats are reserved for the elderly and women with babies.

I reserve judgment on this issue (= I won �t give an opinion on it now) until we have more information.

​ If you reserve something such as a seat on an aircraft or a table at a restaurant, you arrange for it to be kept for your use:

I reserved a double room at the Lamb Hotel.

[ + two objects ] If you get there early, reserve me a seat/reserve a seat for me.

Conserve = to keep and protect something from damage, change, or waste:

To conserve electricity, we are cutting down on our heating.

The nationalists are very eager to conserve their customs and language.

I �m not being lazy - I �m just conserving my energy/strength for later.

Preserve -  to keep something as it is, especially in order to prevent it from decaying or being damaged or destroyed:

to preserve the environment

We want to preserve the character of the town while improving the facilities.

The agreement preserved our right to limit trade in endangered species.

Putting varnish on wood is a way of preserving it.

I need to get out of the house from time to time just to preserve (= prevent me from losing) my sanity.

well preserved - to treat food in a particular way so that it can be kept for a long time without going bad:

preserved fruit

oranges preserved in brandy

More examples

It �s our duty to preserve the planet for future generations.

The Forestry Commission is responsible for preserving over 2 million acres of woodland.

The remains of the Roman fort are well preserved.

Every attempt is being made to ensure that these works of art are preserved for posterity.

He has a collection of prehistoric insects preserved in amber.