Every person you hear talking on TV has a microphone specially set up for them. Someone has to do that, and in fact it is probably the most common sound engineering task out of anything that a sound engineer could possibly do.
In the TV studio, every person who appears on camera will be fitted with a clip-on miniature microphone, usually with a radio transmitter for convenience and freedom from cables (cameras don't like traveling over cables, and they are also trip hazards for non-technical personnel).
If they don't get a clip-on mic, they will have a mic mounted on a desk stand or perhaps a boom mic held over them just out of shot. Occasionally, TV presenters and studio guests get to hold a microphone. This might be because the clip-on mic has failed, which they do occasionally.
All the mics in the studio will be connected through to the sound mixing console. TV consoles commonly have lots of channels – up to 100. This is not so that every channel can be used at the same time, but so that groups of channels can be set up for different segments of a show.
The Sound Supervisor (the title of this position varies with country, but the nature remains the same) will supervise the entire sound team and operate the mixing console. The Sound Supervisor is responsible for the quality of sound on the production.
The type of work in a television studio varies from live talk shows, to recorded 'as live' productions, through to soap opera and, at the high end, quality comedy and drama. The work is fast paced and everyone is expected to get it right first time. For instance, where a film shoot might require several takes to get a shot right, the nature of soap opera production means that to retake a shot due to a technical problem results in frowning faces all round.
In television there is a good career structure. You can start by clipping on microphones, work up to sound supervisor on small productions, then move to increasingly prestigious production companies and broadcasters as your status in the industry develops.