The Hebrew letter ס (samekh) at the end of a verse in a digital (on-line) Tanakh (e.g., Mechon-Mamre.org) signifies a סתומה (setuma) in a Tanakh scroll (e.g., Aleppo Codex).
For example, Song of Songs 1:14.
Online Tanakh (Mechon-Mamre.org):

Tanakh scroll (Aleppo Codex):

While a Hebrew letter פ (fe) at the end of a verse in a digital (on-line) Tanakh signifies a פתוחה (petucha) in a Tanakh scroll.
For example, Song of Songs 1:4.
Online Tanakh (Mechon-Mamre.org):

Tanakh scroll (Aleppo Codex):

According to Chabad.org,
In terms of Jewish law, the word parshah refers to a set of verses that is written in the Torah scroll without any break within the text. Depending on how big the space needs to be before a particular parshah, it is called a parshah petucha, “an open portion,” or a parshah setuma, “a closed portion.” The text of “an open portion” always begins on a new line on the parchment, and “a closed portion” can begin even on the same line, after an empty space equaling the width of as few as nine letters from the previous portion.1
In our printed versions of the Torah, the chumash, the place where an “open portion” would appear in the Torah scroll is marked with the Hebrew letter pei (Heb. פ), and a “closed portion” is marked with the letter samech (Heb. ס).
The ׃ is a סוף פסוק (sof pasuk) which indicates the end of a verse.
Per Wikipedia,
The Sof passuk (Hebrew: סוֹף פָּסוּק, end of verse, also spelled Sof pasuq and other variant English spellings, and sometimes called סלוק silluq) is the cantillation mark that occurs on the last word of every verse in the Tanakh.
I don't see these in the Aleppo codex, so either the scribe didn't use them in that particular manuscript, or they are only incorporated in digital (online) Tanakhs.