Liquid manure is also known as manure tea. This type of manure is useful for providing water-soluble nutrients quickly to plants that grow quickly, such as summer vegetables.
Liquid manure made by infusing raw animal manure that has not been composted is considered inferior (and potentially unsafe) by many organic gardeners and many will not not use it. This has to be balanced with the simplicity of making it and when made from well-rotted ruminant (usually cow) manure, it can be made safely.
For the best benefits, liquid manure should be combined with plants that have beneficial nutrients for the soil and growing new plants. Typical plants to add include wormwood, neem, garlic, marigold, nettle, lemongrass, comfrey, etc.