Trying to simplify Inuyasha is like trying to use a toothpick to chip away at a statue...a gaudy, broken statue that smells of flatulence...but I'll try. I'll break it into steps to make it easier for me to choke it down, er, you to remember.
*Spoilers*
1. Inuyasha - super powerful half-demon (not hard to picture, since most anime is practically about super powers or mechs). He's in love with a human woman (Kikyo), forming the crux of the show and she shows up tons of times. Her appearances coincide with the RARE attempts of the show at having a plot or being any good.
2. Kagome - an annoying, whiny, jealous, but otherwise "pure hearted saint" of a female...then add in the fact she is given the abitrary role of "chosen one," with the ability to do all that purifying, sanctity, and superpower BS. Then add on top that she's embroiled in the "love triangle" that dominates half of the story. She also has the ability to "dominate" Inuyasha too. "SIT" makes him fall to the ground. Think of it the same running joke as "Gay Stewie" in Family Guy or "Ed is Short" in Fullmetal Alchemist. All forms of stupid humor that gets thrown in EVERYWHERE!
3. Other characters tag along. Sadly, after their initial arcs, their roles get boiled down to "support comic relief." Another long running gag involves Miroku grabbing Sango's ass every three episodes or so. Along with Kikyo, Sesshomaru (Inuyasha's brother) shows up to reminds us how much everyone else in the show sucks balls. Maybe it's because he's the "anti-hero/villain badass," but in a show about a stupid teenage girl dominating a demon, something has to give.
4. The main villain has a tendency of getting chased, then found, then escape, then get found again, then get killed, just to revive, to DO IT ALL AGAIN!
5. The show is littered with terrible writing and plot. It's like the anime equivalent of Eternal Sonata. Characters CONSTANTLY reiterate the main plot points (even in filler episodes). Story arcs (like the love triangle) get played out multiple times in different stretches...to the same boring ass results. The most annoying of all flubs was the main characters constantly yelling each others names. That happens every time someone gets kidnapped, runs off, leaves pissed, or whatever. It got so bad that Adult Swim made a legendary commercial spoof. It's similar to the "RENA" "SHUGO" yelling in .hack//Legend of the Twilight. Both cases suck balls.
6. Normal anime series stretch to 26-52 episodes. They sometimes issue filler, but they tend to be short forays. Inuyasha stretched 170 episodes, plus 4-5 movies, THEN another series. That's Naruto/Bleach/Ranma territory. Don't forget that the revolving "death/revival/love triangle" plot twists rear their heads every 20-30 episodes, THEN normal filler, THEN character specific filler episodes on top of that...then a bunch of **** about baby demons with mind control powers, drunk Buddhist monks, talking fleas getting married, and other dumb crap.
If that doesn't hope to steer you away from the show, nothing will. I got out after episode 130. I almost feel ashamed for sticking with it that far. The damage that show has caused will NEVER go away.