#define에서 문장의 중간에 나타나는 #의 의미는?

#define TRACE(l,s)      { if (CheckTraceLev(l)) { TrcPrintf_##l s ; } }

#if ( defined (__GNUG__) && defined (_SYSTYPE_SVR4) ) || defined (__UNIX__)
#include <syslog.h>
#else
#define  LOG_EMERG     0  // An extreme emergency
#define  LOG_ALERT     1  // A condition that should be corrected immedialtely
#define  LOG_CRIT      2  // A critical condition like a hardware error
#define  LOG_ERR       3  // An error that require attention but is not critical
#define  LOG_WARNING   4  // A warning that an error condition may exist
#define  LOG_NOTICE    5  // A condition tha in not an error, but may need
                          // attention
#define  LOG_INFO      6  // An informational message (e.g., a message issued 
                          // when a server starts execution)
#define  LOG_DEBUG     9  // A message used by programmer for debugging
#endif

int  EXPORT TrcPrintf_LOG_EMERG   (const char *fmt, ...);
int  EXPORT TrcPrintf_LOG_ALERT   (const char *fmt, ...);
int  EXPORT TrcPrintf_LOG_CRIT    (const char *fmt, ...);
int  EXPORT TrcPrintf_LOG_ERR     (const char *fmt, ...);
int  EXPORT TrcPrintf_LOG_WARNING (const char *fmt, ...);
int  EXPORT TrcPrintf_LOG_NOTICE  (const char *fmt, ...);
int  EXPORT TrcPrintf_LOG_INFO    (const char *fmt, ...);
int  EXPORT TrcPrintf_LOG_DEBUG   (const char *fmt, ...);
int  EXPORT TrcPrintf_MAX_TRC_LEV (const char *fmt, ...);
int  EXPORT TrcPrintf_MIN_TRC_LEV (const char *fmt, ...);

int  EXPORT TrcPrintfDeb (int x, const char *fmt, ...);
int  EXPORT TrcPrintfTst (int x, const char *fmt, ...);
int  EXPORT TrcPrintfRel (int x, const char *fmt, ...);


int  EXPORT CheckTraceLev (const int level)
{
    return (CurTraceLev = level) <= TraceLevel;
}

// Logger 호출부분
TRACE(LOG_INFO,("File: %s version %s compiled on %s %s",file,id,date,time));

위의 소스에서 #define TRACE(l,s) { if (CheckTraceLev(l)) { TrcPrintf_##l s ; } }의 "#"이 뭘 의미하는 건가요???
C++은 그리 많이 사용해 보지 않아서.. 의미파악이 힘드네요..