What is the key word “Snowball” mean in Elastic search?

Question

When i'm using elastic search , i've to indecies it first. In this process i blindly using "SNOWBALL" , "KEYWORD" n analyzer coloumn. What is the main use of Analyzer (I know it is a booster) but it helps me in elastic search n What is the key word "Snowball" mean?

'data.description': {'analyzer': 'snowball', 'type': 'string'},
'data.title': {'analyzer': 'snowball', 'type': 'string'}