# What does "mass" mean in a Macroeconomic model?

A Solow model problem I am trying to solve asks me to assume that the economy consists of identical agents of mass 1. I have never heard of this term before, what does this mean?

If you work in a continuous setting, you have an infinite number of agents, which lie on a line between $$0$$ and $$M$$. Let's say individual consumption is given by the function $$C(i)$$, for all agents $$i \in [0,M]$$.
For total consumption, you have to integrate: $$C = \int_0^M C(i)di$$ (total consumption is the area under the graph). $$M$$ is the mass of all agents. In your example, $$M$$ is equal to 1.