70 Mustang
Glideslope and localizer, aka "raw data." They show only your angular deviations from the horizontal and vertical perfect positions. If you're right of course see a "fly left" needle, it's up to you to turn left just the right amount, then level the wings, then turn right at just the right time and just the right amount, so you re-intercept the course without blowing through it. If you see "fly left" and simply turn left until it's centered, you're virtually guaranteed to blow left through the course at a severe angle. Shown as a pair of needles over the DG on old simple planes (think 1970's 172), or (on a HSI) the middle split out part of the course needle (for the localizer, same as the VOR course function) and diamond or triangle on one (or both) side(s) moving up and down (for the glideslope.) On standby ADI's that have it, pair of needles over the standby ADI. Probably never over a main ADI.
Flight Director. Tells you to fly left/right, or up/down, but with none of the planning and finesse required by the raw data. The computer does your thinking for you. If you're right of course and see a "fly left," you can follow it stupid as a monkey, and it will show a fly-left to guide you into the initial left bank, then show centered when you should level your wings, and show a fly-right to guide you into a bank to the right to make a perfect intercept. Shown as either a pair of needles, or an upside down V shape for you to slot a triangle into, over the main ADI. Probably never in the history of aviation shown over a standby ADI.