Adepicts the flow of carbon through an ecosystem, whereas a depicts the transfer of energy.

A Food chain and energy pyramid.

The food chain potrays how organisms relate to one another in a ecosytem beginning with the producers that incorporate carbon into the ecosystem through photosynthesis. Primary consumers consume them and, the chain progress to tertiary consumers and decomposers.
The energy pyramid portrays the transfer of energy in an ecosystem by showing the energy levels as biomass levels and their transfer to upper levels. The first image on the left is a food chain while that on the right depicts an energy pyramid.

No its just makes the straight guy curious