(Follow-up to MaplePanda's answer)

Do not confuse the shift outer cap with long tongue (bottom of the first image below) with the outer cap with short tongue (top of the first image).

The shift outer cap with long tongue is used to weather-proof rear shifting stop sand/dust from entering the cable cover.

The outer cap with short tongue, as you see in an excerpt from a Shimano Dealer's Manual, is the end of the Bowden cable that sits against the brifter.

In addition to having a long or short tongue, another difference is that the outer cap with short tongue has a slant-cut short tongue and a notch that stops it from rotating, to ensure that the slant-cut tongue is properly positioned.

(Follow-up to MaplePanda's answer)

Do not confuse the shift outer cap with long tongue (bottom of the first image below) with the outer cap with short tongue (top of the first image).

The shift outer cap with long tongue is used to weather-proof rear shifting by stopping sand/dust from entering the cable cover.

The outer cap with short tongue, as you see in an excerpt from a Shimano Dealer's Manual, is the end of the Bowden cable that sits against the brifter.

In addition to having a long or short tongue, another difference is that the outer cap with short tongue has a slant-cut short tongue and a notch that stops it from rotating, to ensure that the slant-cut tongue is properly positioned.