Sharing, most of the times, refers to the joint use of a resource. It can also mean other different things to different people such as:
to have in common
Sharing is an offer or an agreement that is not asking for property in exchange. The outcome of the agreement could either be a small environtment of freedom for using a single thing (or asset) (i.e. let's share the pen), a bigger scope context (i.e. a global system for distributed allocation of resources) or a more abstract things (shared meaning, sharing values) through the same practice.
Sharing creates opportunities for mutual care between people by lowering the implicit authority there is in ownership. The owner, by the act or the declared fact of being sharing or willing to share his thing (or his ownership rights), is admitting that is not going to use his asking for property royalties force / rights during sharing.
Here, at sharewiki, we are not going to draw a very strict line on what is or what is not sharing while at the same time you'll find pages like this one and others where the sharing line is much more defined than at plain sharing.
There's not always somebody to share with, and you are right thinking that other people could take advantages on you when you are ready to share something. That's why you should moderate your sharings. Just keep in mind that tending and living in the consciousness of being open to share creates the possibility to change (y)our world from the first moment you let that vibe being spread inside you.
"a person who does not share is not only selfish, but bitter and alone." - Paulo Coelho
By allowing others to use your things, you can maximize development possibilities for those things and others that will show up after that. By sharing, we could experience a more social life for a more abundant enjoying than the way proposed by the the capitalist scarcitism logic, which is just an appeal to fear fallacy.
Public Private Property
Public Private Property is a proposal for effective sharing of physical goods.
The name PPP ("Public Private Property") is choosen because the private owner keeps the good's property rights and/but decides to establish public co-usage's terms for it.