Wikipedia is your friend:
See also: Four tones
The Qieyun classified characters in four parts according to their tone: even tone (píngshēng 平聲), rising tone (shǎngshēng 上聲), departing tone (qùshēng 去聲), and entering tone (rùshēng 入聲). The "entering tone", also known as a "checked tone", actually refers to syllables characterized by a final stop consonant (/p/, /t/, or /k/) rather than a distinct pitch.
It is difficult to determine the exact contours of the other tones. Karlgren interpreted the names literally as level, rising and falling pitches, respectively. The oldest known description of the tones is found in a Song dynasty quotation from the early 9th century Yuanhe Yunpu 《元和韻譜》 (no longer extant): "Level tone is sad and stable. Rising tone is strident and rising. Departing tone is clear and distant. Entering tone is straight and abrupt."[m]
Every topolect has their own ancient Chinese as well. For example 四川话 has 蜀语 as its "Classical Chinese" - so your assumption that ancient Chinese is root of all modern Chinese would be wrong. Chinese has a lot of variants - that does not mean that they stem from each other or that they are strictly speaking even dialects.
入声 was originally considered a tone - it is your so-called "coda" as you can see from the quote from Wikipedia above. This can still be found in a few Sinitic topolects today, which you obviously already know.