One of the first differences observed with Agile is the way we estimate the size and duration of an IT project.
The entire team is made responsible for the estimate of the product Backlog (the list of all functionality desired in the product). Indeed, the team is invited to estimate collectively this list of valuable items that will require his work.
Scrum teams use Story Points and Planning Poker for this activity.

Planning Poker Deck
Collective intelligence is the pillar of this new way to estimate … an effective team-based estimation technique but not so natural at first. Relative size and consensus are not so easy for the teams new to agile.
Teams often lose the thread of their estimates. They have difficulty in comparing or lack of benchmarks.
Use a visual display of the planning poker values in columns, and place the user stories in the appropriate column during the activity.

Visual display of the estimates