...

Agile is a framework for a way of working in which: 

• experts are empowered, to take ownership and create high-quality solutions,
• the gap between IT and Business is bridged, through input and validation by a business-representing Product Owner,
• transparency, alignment and early escalation (asking for help) are key,
• short cycles lead to adapting and improving plans,
• and we experiment with process improvements to gain efficiency.

...

For this reason work with large estimates is broken down into smaller, workable pieces (that we can still test to validate a piece), and re-estimated.

A recommended tool/game for estimating together with a group is: https://planningpokeronline.com/

Sprinting or Continuous Flow

...