zeogold: In my opinion, all games that are billed as "adventure" should be the point-and-click/puzzle-solving type, whereby you're a character who goes around talking to people and collecting inventory and such.
Originally adventure games were not point&click, but type&type.
I guess there are just a historical reasons why "games where you solve puzzles in some kind of world" is called adventure games. Probabably the first widely known such game was ADVENT (stands for "adventure" with a 8-character limit), as you are adventuring there trying to find a pirate treasure.
So I guess such games where you wander around in a game world solving puzzles were thought as "games like ADVENTure" or simply "games where you are adventuring in a game world, instead of shooting aliens in space or jumping over rolling barrels on platforms". Hence it made sense to start calling such non-space shooter etc. games as "adventure games". It was the first game genre where you do "adventuring" so it reserved that broadly vague and generic term.
Then later people got to know different types of "adventuring games" like the Wizardry and Ultima series, games that are also about "adventuring in a game world" but with stats and fighting enemies too, and less about puzzles to solve. They were to be called "roleplaying games" because of the characters you created for and played in the games, and I guess the slight resemblence to pen%paper RPGs (the stats). Similarly, "roleplaying game" is kind of a vague term too because you play some kind of role in so many games, even in adventure games... but yeah, certain types of games got to reserve that term too.
And so on and so forth... nowadays most games don't neatly fall into certain category, even roughly, but uses traits from many "old genres", hence e.g. action-adventure, action-RPG, tactical RPG, whatever-whatever etc.
But at least we are not talking about "Doom-clones" anymore when we mean FPS games... Many modern gamers don't even know what Doom is.