change the flag description

cmd/utils/flags.go

@@ -274,8 +274,16 @@ var (
 	}
 	defaultVerifyMode   = ethconfig.Defaults.TriesVerifyMode
 	TriesVerifyModeFlag = TextMarshalerFlag{
-		Name:  "tries-verify-mode",
-		Usage: `tries verify mode: "local: a normal full node", "full: state verification by verify node which has diffLayer of blocks", "insecure: state verification by verify node which has no diffLayer of blocks", "none: no state verification"`,
+		Name: "tries-verify-mode",
+		Usage: `tries verify mode: 
+				"local(default): a normal full node with complete state world(both MPT and snapshot), merkle state root will 
+				                 be verified against the block header.", 
+				"full: a fast node with only snapshot state world. Merkle state root is verified by the trustworthy remote verify node 
+					   by comparing the diffhash(an identify of difflayer generated by the block) and state root.", 
+				"insecure: same as full mode, except that it can tolerate without verifying the diffhash when verify node does not have it.", 
+				"none: no merkle state root verification at all, there is no need to setup or connect remote verify node at all,
+				       it is more light comparing to full and insecure mode, but get a very little chance that the state is not consistent
+						with other peers."`,
 		Value: &defaultVerifyMode,
 	}
 	OverrideBerlinFlag = cli.Uint64Flag{