This is hard without defined terms. People use the word "miners" interchangeably. Miner can refer to an organization that mines #Bitcoin or it can refer to an individual machine. For this instance I will use "machine" to describe individual hashing machines and "miner" to mean the person/organization behind the machines.

Hashrate increasing means that more machines are being turned on, whether that's a big miner like Riot or Marathon getting in a new shipment of machines, or individual miners turning on more machines to try their luck solo, or pointing towards ocean.

Each machine has a hashrate, ie 110TH/s (tera-hash per second) so if the global hashrate is going up, it's because more of these machines are going online.