Weak Consistency
After a write, reads may or may not see it. Usually used with VOIP, Video Chat or Multiplayer games where loosing connection is not a big loss.
Eventual Consistency
After a write, your reads are eventually consistent (usually within a few miliseconds) and updated asynchronously. This pattern is used when you need your system to be highly available like DNS, Email, social media apps.
Strong Consistency
After write, your reads will see it. Used when you have to have 100% assurance that your data is correct. Used in banking, ecommerce, ticket apps