The book of Joel is all about a disaster caused by a swarm of locusts. In that context it is talking about God saving the people from the resulting devastation. When we talk about salvation, however, Christians traditionally only mean saving people from sins or maybe saving them so that they can get into heaven. What I'm trying to say is that we need to watch that we don't make our understanding of salvation too small. Salvation is coming alongside a family that has been devastated by a locust swarm or some other kind of economic disaster and helping them to get what they need to start over again because that is what Joel was talking about.
Salvation can also mean all different sorts of healing.
Did you know that when the Christian Gospels talk about Jesus healing various people of many diseases it uses the same Greek word that is translated as saved . Salvation, in other words, can be many things. You can understand it in purely spiritual terms but you can also understand it in very physical terms. If someone is starving, salvation is food. If someone is homeless, salvation is four walls and a roof or the means to get it.