What is the difference between talk with people and talk live with people? I think all kinds of talk is live. If so, why we would say talk live with people?
'Talk live' is used in the broadcast media industry to differentiate between real time interviews and pre-recorded content. The term can also mean have a talk 'in person', as opposed to over the phone, via email, or texting.
The word "talk" has a number of meanings. It can, for example, mean to persuade by any means. It can mean to exchange ideas by any means. For example, one could describe this site as a place people talk about English, although no lip movements are needed and no sounds are exchanged. Two people could even talk by means of recorded messages.
However, for something to be "live" requires one of two things to be the case. Something can be "live" if it was done in real time or in front of an audience. So a live concert is one that wasn't pre-recorded or engineered in separate tracks and then mixed.
Also, something can be "live" if it is happening as you are observing it. You can watch a live concert a day after it happened. And you can be watching a television feed live while the feed carries a pre-recorded program.
I have heard Feynman's talk on quantum physics. It was a live talk, but I've never heard it live.
In summary, if you "talk live", that makes it clear that the metaphorical uses of "talk" are not what you mean and also that a delayed exchange of recorded messages is not what you mean. In a sense, it means that you really mean talk and aren't using using it to exaggerate a level of immediacy that is not actually present.
Essentially, you're saying that you recognize that people describe all kinds of things that aren't really talking as a "talk with people" and that's not what you mean. You mean the real, deal -- actual live talking.