Lime is mainly useful for vegetable gardens. As you constantly put on compost, your soil is gradually acidified, and most vegetables prefer neutral or alkaline soil.
Adding a handful of lime to a square metre therefore helps redress this balance. Lime also helps break down compost and manure and release the nutrients in the soil to make them available to the plants.
NEVER mix fresh manure and lime though, and don't overdo the amount you use. Too much lime and you can rob the soil of nutrients.

Before you start though,have you tested your soil to find out whether it is acid ?If it is alkaline (pH 7)you will not need lime at all. You can buy a pH metre at most good garden shops. If rhododendrons do well in your area and most hydrangeas are blue it is probably acid. If most hydrangeas are pink it is probably alkaline, in which case lime will be useful on your veg patch. But keep it away from acid loving plants such as rhododendrons, pieris, skimmia, calluna.
An old gardener I knew taught me to dip brassica seedlings in lime before planting out to prevent club root.

Thank you for your useful advice, Steragram. I will bear it in mind.