It means to explain the issue or the problem so that another person can understand (and, perhaps, provide advice). It is sort of a metaphor. "Lay out" means to place something on a table or on the ground so that it can be easily seen. (Example: I"m going to lay out three dresses on the bed for you to choose from). SImilarly, when you "lay out" a problem or an issue, you show someone all the parts of the issue or problem so that they can understand it and make a decision.

その分で「lay out」の意味は「説明する」です。口語英語です。 "Lay out" means to "state clearly" or "explain" the issue. You might also hear more elaborate variations like "She laid it all out" but still meaning "She explained it all." You might even hear someone say "He'll lay it all out on the table." Again, the meaning is basically the same. These are all colloquialisms, so you can use them or not use them and be fine either way. But, you probably will hear native speakers say something like this from time to time. We don't usually write them, however.