Weird Crashes

I opened up my launcher like usual, and I pressed PLAY. It took a few seconds then this message came up:

//Hi, I'm Minecraft, and I'm a crashaholic.
[19:10:45] [Client thread/INFO]: Setting user: xPH03NIXx
[19:10:45] [Client thread/INFO]: (Session ID is token:a84da97475454a2aae570c85868eaf96:74368717ca674a7a8ca4a18e488bc953)
Exception in thread "Client thread" com.google.gson.JsonSyntaxException: java.lang.IllegalStateException: Expected BEGIN_ARRAY but was STRING at line 1 column 1
at com.google.gson.Gson.fromJson(Gson.java:815)
at com.google.gson.Gson.fromJson(Gson.java:768)
at ry.b(SourceFile:148)
at ry.<init>(SourceFile:42)
at net.minecraft.server.MinecraftServer.<init>(SourceFile:155)
at cyk.<init>(SourceFile:40)
at bsu.<init>(SourceFile:282)
at net.minecraft.client.main.Main.main(SourceFile:120)
Caused by: java.lang.IllegalStateException: Expected BEGIN_ARRAY but was STRING at line 1 column 1
at com.google.gson.stream.JsonReader.beginArray(JsonReader.java:338)
at com.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.read(CollectionTypeAdapterFactory.java:79)
at com.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.read(CollectionTypeAdapterFactory.java:60)
at com.google.gson.Gson.fromJson(Gson.java:803)
... 7 more
Java HotSpot(TM) 64-Bit Server VM warning: Using incremental CMS is deprecated and will likely be removed in a future release

I don't know what this means, so can you explain?