What does "knights have no long-lasting support points" mean in this game? In this article on pawn structure, the author uses this game as example:

[Event "Prague 2008"]
[Site "?"]
[Date "????.??.??"]
[Round "?"]
[White "David Navara"]
[Black "Vladimir Kramnik"]
[Result "0-1"]
[SetUp "1"]
[FEN "rnbq1rk1/pp2bppp/2p5/2npP3/3N1P2/2NB4/PPP3PP/R1BQ1RK1 b - - 0 9"]
[WhiteElo ""]
[BlackElo ""]
[ECO ""]
[CurrentPosition "rnbq1rk1/pp2bppp/2p5/2npP3/3N1P2/2NB4/PPP3PP/R1BQ1RK1 b - - 0 9"]

9...Nxd3 10.Qxd3 f5! 11.Nb3 Na6 12.Be3 Nc7 { Defends d5 (making ...c5 possible) and, at the right time, move the knight to e6. } 13.Ne2 b6 14.Nbd4 Ba6 15.Qd2 Qe8 16.c3 c5 { The d4-knight is pushed back to the cold, dark, hellish vistas that occurs when you realize that you’ve been thoroughly outplayed. } 17.Nf3 Rd8 18.Rfd1 Ne6 { and Black has created a dream for Black. Here’s the rest of the game: } 19.a4 h6 20.a5 Qb5 21.Ng3 bxa5 22.Qc2 g6 23.Qa4 Qxa4 24.Rxa4 d4 25.cxd4 cxd4 26.Nxd4 Bc5 27.Rxa5 Nxd4 28.Rxa6 Nf3+ 29.Kf2 Bxe3+ 30.Kxf3 Rxd1 31.Kxe3 Rfd8 32.Rxg6+ Kh7 33.Ra6 R8d3+ 34.Kf2 R1d2+ 35.Ne2 Rd7 36.e6 Rb7 37.Ke3 Rdxb2 38.Nd4 R2b6 39.Rxb6 Rxb6 40.e7 Rb8 41.Nxf5 a5 42.Nd4 a4 43.Nc6 Re8 44.Kd4 Kg7 45.Kc4 Kf7 46.Kb4 Ra8 47.Ka3 Ra6 48.Nb4 Rd6 49.Kxa4 Kxe7 50.Kb5 Rd2 51.g4 Rxh2 52.Kc5 Ke6 53.Kd4 Rh4 54.f5+ Kf7 55.Ke5 Rxg4 56.Nd5 Ra4 57.Nc3 Rb4 58.Ne4 h5 59.Ng5+ Kg8 60.f6 h4 61.Kf5 Rb5+ 62.Kg6 Rxg5+ { , 0-1 }  0-1


Then, when explaining why 10... f5! is a good movement, he says:


  The idea is that White’s knights have no long-lasting support points


What does this mean? how does the pawn on f5 achieve or help to this?
It is not that the pawn on f5 achieves/helps this. As far as I understand Silman, what he means is that black can play 10...f5, which gives white a protected passed pawn and which weakens the square e6, because white's knights will eventually be driven away when black plays c5, etc

Look at the position after 18.... Ne6 for instance. Black has achieved everything he wanted: blocked the passed pawn with his knight, gained space in the center through his pawns on c5 and d5, has a very strong bishop on a6.... The white knights on the other hand have no good squares  to go to and also the other pieces of white don't do much.

Consider the opposite situation, where the white knights could not be driven away (i.e. where they have long-lasting support points). For instance if white had a (protected) pawn on c5 in the initial position, black would have a very hard time after f5 because the knight on d4 attacks f5, c6 and hinders black from blocking the passed pawn by placing a piece on e6. It also hinders black from play on the queenside (because the c6 pawn might be weak or hanging). Furthermore the second white knight could be moved to e3 further adding to the pressure.

So essentially what Silman is saying is that Kramnik can play 10...f5 which is against the principle of not giving your opponent protected passed pawns, because in this situation here, white cannot make use of this asset. The knights will be kicked away and black's play on the queenside is more valuable than the protected passed pawn, which often only pays off in an endgame.