There are two different type of conservation: remedial and preventive.
Remedial (or 'interventive') conservation is the process of cleaning and making sensitive repairs to objects to reveal original surfaces, restore meaning and strengthen fragile components. This process makes objects much more stable and therefore more able to withstand being on display and handled.
Preventive conservation is the control of the physical environment in which objects are displayed and stored, in order to prevent degradation of the materials from occurring in the first place. Objects require a stable relative humidity and temperature within certain specifications, dependent upon their materials. Visible light, ultraviolet light, other pollutants and insect pests need to be controlled to maintain the collection.