Wikipedia's Chess Opening entry

From the wiki above:

Top-level objectives[edit]

At higher levels of competition, for many years the main objectives of opening play were to obtain the better position when playing as White and to equalize when playing as Black. The idea behind this is that playing first gives White a slight initial advantage; for example, White will be the first to attack if the game opens symmetrically (Black mirrors White's moves).[5]

Since about the 1950s another objective has gradually become more dominant. According to IM Jeremy Silman, the purpose of the opening is to create dynamic imbalances between the two sides, which will determine the character of the middlegame and the strategic plans chosen by both sides.[8] For example, in the main line of the Winawer Variation of the French Defense (1.e4 e6 2.d4 d5 3.Nc3 Bb4 4.e5 c5 5.a3 Bxc3+ 6.bxc3), White will try to use his bishop pair and space advantage to mount an attack on Black's kingside, while Black will seek simplifying exchanges (in particular, trading off one of White's bishops to blunt this advantage) and counterattack against the weakened pawns on White's queenside; both players accept different combinations of advantages and disadvantages. This idea was a doctrine of the Soviet school of chess.

A third objective, which is complementary to the previous ones and has been common since the 19th century, is to lure the opponent into positions with which the player is more familiar and comfortable than the opponent. This is usually done by transpositions, in which a game that apparently starts with one opening can reach a position that is normally produced by a different opening.[6][7]

In Kotov's Train like a Grandmaster he refers to 3 ways of playing with White: the first is to quietly maintain his slight birthright edge (if not needing to win at all costs) - this corresponds to what's in the first wiki paragraph above; the second way is to play with an independent plan from Black - this corresponds to what's in the second wiki paragraph above; the third way is the method of the coiled spring (such as in the King's Indian Attack), where White hopes to build up a sort of potential energy - perhaps this is akin to what in Chess for Zebras GM Jonathon Rowson calls 'potential' (referring to [at least] one of the two armies having it).

In The Caro-Kann, second edition, by Jouska, she opines that due opening theory being expanded (especially by computer use), White 'no longer is content to play a position as it is' (I guess meaning always trying to play objectively best moves and/or maintain the birthright slight edge, though I'd contend this is still a perfectly current way[s] of playing, even at elite level perhaps), and instead now tries to play one of three ways: A) try to blast Black off the board; B) attempt to force Black to grovel for a draw in a chanceless position (such as in many queenless middlegame positions, I'd guess); else C) attempt to catch Black in unfamiliar territory (corresponds to the 3rd wiki paragraph above, though perhaps she's not thinking about mainly transpositional possibilities, and indeed this could be a flaw of the 3rd wiki paragraph's description).

I'd suggest that, even if White starts off a game with a definite way to play in mind, as described in any of the paragraphs above, Black could have his own ideas on how to define the character of the game in spite of White's hopes, if Black gets a chance at some point, never mind any mistakes first being required(!)