In this chapter, Ruth goes out to glean in the fields during harvest.
This is another interesting chapter. The reason why I like this chapter is that it shows how Israelite customs formed in response to commandments from the Law. Leviticus 19:9 (and 23:22) says that the Israelites must not reap the corners of their fields, nor are they permitted to pass over the field twice. Deut 24:19-21 gives this command in an even more extended way, saying that whether reaping wheat or olives or grapes, the harvesters should only pass over it once and leave the rest for the widows and orphans.
The practical result is what we see in this chapter. People like Ruth, who did not possess fields of their own to sow and harvest, would go to other people's fields and follow after their harvesters, gleaning from what is left over. And I don't think it was just Ruth doing this, it became a tradition in Israel that those in poverty could go out and gather after the reapers, essentially collecting the second harvest from what was left behind.
Even so, this was a dangerous thing for a woman and a foreigner to do alone. Naomi permitted Ruth to do this in verse 2, but they didn't have any other source of food. Without gleaning in the fields, they would have nothing. Also, I think it's pretty clear that not every field owner would permit this. It's part of the Law, but there are many Israelites in this time who did not obey the Law.
Boaz goes beyond the Law, though. He provides Ruth water drawn from his wells (v. 9), gives her food prepared for his servants (v. 14), and even goes so far as to tell his harvesters to deliberately leave behind grain for Ruth to harvest (v. 16).
When Ruth returns to her mother-in-law, Naomi seems amazed at how much Ruth was able to gather, because Boaz favored her and asked his servants to help her.
So there are a couple things going on here. The first is what I already mentioned, that Ruth is taking on the risk of physical harm by going out from Bethlehem into the surrounding fields to glean (see e.g. verse 22). The second is this fortuitous meeting of Ruth and Boaz. The third is Boaz's kindness to Ruth, with Boaz helping Ruth because of "all that you have done for your mother-in-law after the death of your husband". It seems that Boaz is a decent guy, but also helps Ruth because of their family relationship through Naomi. This is in spite of Ruth being a Moabite and a foreigner.
Things in the story are starting to look up.