getaddr.bitnodes.io shows only the reachable Bitcoin nodes in the network. These are nodes that make up the core data exchanges within the P2P network.

There is non-trivial distinction between mining and non-mining nodes at the protocol level among the network participants. Although having observed the first announcement of a block from a node may be a good indicator of a mining node.

It is impossible to tell the full size of the network that includes nodes behind firewall, or nodes that only accept connection from certain IP address/netblock, or nodes that have simply hit the set max. connections.