Basic meaning: doing a thing to send a message about yourself to others. Like wearing expensive brands to signal that you're rich.
But good signalling involves some additional factors. Signalling is usually used when you want to say something about yourself, but it's something that people would want to say about themselves whether it was true or not, so you have to say it in a way that is difficult or impossible to fake. A good signal is one that is highly visible (in the context where it matters; clothes are good for in-person signaling, profiles or photos are good for online signaling), and either cannot be sent without having the quality they're supposed to signify (you can't afford expensive things to show off if you don't have money), or are much easier to send if you have that quality than if you don't (it's easier to get a high StackOverflow score if you're good at programming and communicating than if you're not).
If you're giving employees extra stock to signal loyalty and trustworthiness, it's "cheaper" to do that if you actually value being loyal and trustworthy (rather than just wanting others to think that of you), because then you get value from being the sort of person you want to be and being thought well of by others. At least, that's the theory; you could just want other people to think you're a loyal person really, really badly.
But good signalling involves some additional factors. Signalling is usually used when you want to say something about yourself, but it's something that people would want to say about themselves whether it was true or not, so you have to say it in a way that is difficult or impossible to fake. A good signal is one that is highly visible (in the context where it matters; clothes are good for in-person signaling, profiles or photos are good for online signaling), and either cannot be sent without having the quality they're supposed to signify (you can't afford expensive things to show off if you don't have money), or are much easier to send if you have that quality than if you don't (it's easier to get a high StackOverflow score if you're good at programming and communicating than if you're not).
If you're giving employees extra stock to signal loyalty and trustworthiness, it's "cheaper" to do that if you actually value being loyal and trustworthy (rather than just wanting others to think that of you), because then you get value from being the sort of person you want to be and being thought well of by others. At least, that's the theory; you could just want other people to think you're a loyal person really, really badly.