Plz any one help me in understanding this code

Private Declare Function waveOutGetPosition Lib "winmm.dll" (ByVal hWaveOut As IntPtr, ByRef lpInfo As MMTIME, ByVal uSize As Integer) As Integer
Private Declare Ansi Function waveOutOpen Lib "winmm.dll" (ByRef hWaveOut As IntPtr, ByVal uDeviceID As Integer, ByVal format() As Byte, ByVal dwCallback As WaveDelegate, ByRef fPlaying As Integer, ByVal dwFlags As Integer) As Integer
Private Declare Function waveOutPrepareHeader Lib "winmm.dll" (ByVal hWaveIn As IntPtr, ByRef lpWaveInHdr As WAVEHDR, ByVal uSize As Integer) As Integer
Private Declare Function waveOutPrepareHeaderPtr Lib "winmm.dll" (ByVal hWaveIn As IntPtr, ByVal lpWaveInHdr As Integer, ByVal uSize As Integer) As Integer
Private Declare Function waveOutReset Lib "winmm.dll" (ByVal hWaveIn As IntPtr) As Integer
Private Declare Function waveOutUnprepareHeader Lib "winmm.dll" (ByVal hWaveIn As IntPtr, ByRef lpWaveInHdr As WAVEHDR, ByVal uSize As Integer) As Integer
Private Declare Function waveOutClose Lib "winmm.dll" (ByVal hWaveIn As IntPtr) As Integer
Private Declare Function waveOutWrite Lib "winmm.dll" (ByVal hWaveOut As IntPtr, ByRef lpWaveOutHdr As WAVEHDR, ByVal uSize As Integer) As Integer
Private Declare Function waveOutPause Lib "winmm.dll" (ByVal hWaveOut As IntPtr) As Integer
Private Declare Function waveOutRestart Lib "winmm.dll" (ByVal hWaveOut As IntPtr) As Integer
Private Declare Function waveOutSetVolume Lib "winmm.dll" (ByVal uDeviceID As IntPtr, ByVal dwVolume As UInt32) As Integer
Private Declare Function waveOutGetVolume Lib "winmm.dll" (ByVal uDeviceID As IntPtr, ByRef lpdwVolume As Integer) As Integer
Private Declare Function mmioClose Lib "winmm.dll" (ByVal hmmio As IntPtr, ByVal uFlags As Integer) As Integer
Private Declare Function mmioDescend Lib "winmm.dll" (ByVal hmmio As IntPtr, ByRef lpck As MMCKINFO, ByRef lpckParent As MMCKINFO, ByVal uFlags As Integer) As Integer
Private Declare Function mmioDescendParent Lib "winmm.dll" Alias "mmioDescend" (ByVal hmmio As IntPtr, ByRef lpck As MMCKINFO, ByVal x As Integer, ByVal uFlags As Integer) As Integer
Private Declare Ansi Function mmioOpen Lib "winmm.dll" Alias "mmioOpenA" (ByVal szFileName As String, ByRef lpmmioinfo As MMIOINFO, ByVal dwOpenFlags As Integer) As IntPtr
Private Declare Function mmioRead Lib "winmm.dll" (ByVal hmmio As IntPtr, ByVal pch As Integer, ByVal cch As Integer) As Integer
Private Declare Function mmioReadString Lib "winmm.dll" Alias "mmioRead" (ByVal hmmio As IntPtr, ByVal pch() As Byte, ByVal cch As Integer) As Integer
Private Declare Function mmioSeek Lib "winmm.dll" (ByVal hmmio As IntPtr, ByVal lOffset As Integer, ByVal iOrigin As Integer) As Integer
Private Declare Ansi Function mmioStringToFOURCC Lib "winmm.dll" Alias "mmioStringToFOURCCA" (ByVal sz As String, ByVal uFlags As Integer) As Integer
Private Declare Function mmioAscend Lib "winmm.dll" (ByVal hmmio As IntPtr, ByRef lpck As MMCKINFO, ByVal uFlags As Integer) As Integer
Private Declare Function GlobalAlloc Lib "kernel32" (ByVal wFlags As Integer, ByVal dwBytes As Integer) As IntPtr
Private Declare Function GlobalLock Lib "kernel32" (ByVal hmem As IntPtr) As IntPtr
Private Declare Function GlobalFree Lib "kernel32" (ByVal hmem As IntPtr) As Integer
Private Declare Function GlobalUnlock Lib "kernel32" (ByVal hmem As IntPtr) As Integer
Private Declare Sub CopyWaveFormatFromBytes Lib "kernel32" Alias "RtlMoveMemory" (ByRef dest As WAVEFORMAT, ByVal source() As Byte, ByVal cb As Integer)
Private Declare Sub CopyWaveHeaderFromPointer Lib "kernel32" Alias "RtlMoveMemory" (ByRef dest As WAVEHDR, ByVal source As Integer, ByVal cb As Integer)
Private Declare Function IsBadWritePtr Lib "kernel32" (ByVal lp As Integer, ByVal ucb As Integer) As Integer
'</API-DECLARES>
Private Delegate Sub WaveDelegate(ByVal hwo As IntPtr, ByVal uMsg As Integer, ByVal dwInstance As Integer, ByRef wavhdr As WAVEHDR, ByVal dwParam2 As Integer)