What is a "bridi"? A bridi is a piece of text. A bridi expresses a relationship.
In order to express a relationship between some referents, each bridi has to contain two basic things: what the relationship is, and what the referents are. The gismu "bridi" is a three part relationship: The first part is the whole bridi, what we call a "bridi" in English, the whole piece of text. The second part, the "se bridi" or "selbri", describes the relationship expressed by the bridi. The third part, the "te bridi" or "terbri", describes the referents that take part in that relationship. So a "bridi" consists of a "selbri" (relationship) and "terbri" (referents).
Here's a simple bridi in Lojban: "mi ti klama", I go there. The "bridi" is the entire text, "mi ti klama". The "selbri" is just "klama". The "terbri" is a list of two things: "mi" and "ti".
Here's another bridi, a compound bridi: "mi cusku lu mi ti klama li'u", I say "I go there". The bridi is the whole text. The selbri is "cusku". The terbri is a list of two things: "mi", and a quotation. The quotation itself contains another bridi, the bridi "mi ti klama" we just discussed, between lu/li'u quotes. Bridi can go inside of bridi to an unlimited depth in Lojban: "mi cusku lu mi cusku lu mi cusku lu mi ti klama li'u li'u li'u", etc. (i say that i say that i say that i'm going)
The main way to make a bridi in Lojban is by using "brivla". Hopefully Lojban's rafsi system will help you avoid terminology overload here: Notice that this is the same root "bri" for "bridi" that we just saw in "selbri". "vla" is for "valsi", word. So a "brivla" is a bridi-word. Gismu, lujvo, and fu'ivla are all brivla. All you need to do in Lojban to give the selbri (the relationship) of a bridi, is to say an unadorned brivla. When you say a brivla in a normal context in a bridi (not after a "lo" or something) then it becomes the selbri of that bridi. For instance if you just say "klama", then you've already made "klama" the selbri and said a full valid sentence (since the terbri is allowed to be empty in Lojban). When you say "mi ti klama", "mi" and "ti" are each put into slots in the terbri (because they're sumti), but when you say "klama", that becomes the selbri and shows what the relationship is between the two things you've just put into the terbri.
Does that make sense to y'all? Any questions?
mu'o mi'e se ckiku