can anyone explain the logic of this afl

_SECTION_BEGIN("ema3,15");
x = EMA(Close,3);
y = EMA(Close,15);

Plot(EMA(Close,3),"",colorBrightGreen, styleLine, styleThick);
Plot(EMA(Close,15),"",colorRed, styleLine, styleThick);
GraphXSpace=0.5;
Plot(C,"",colorWhite,styleCandle);
XR=(EMA(Close,3) * (2 / 6 - 1) - EMA(Close,15) * (2 / 11 - 1)) / (2 / 6 - 2 / 11);


Buy = Close > EMA( Close , 15 )
AND Ref( Close , -1 ) > Ref( EMA( Close , 15 ) , -1 )
AND Cross(x,y);

Sell = Close > EMA( Close , 3 )
AND Open > EMA( Close , 3 );

Short = Close < EMA( Close , 3 )
AND Ref( Close , -1 ) < Ref( EMA( Close , 3 ) , -1 )

AND Cross(y,x);

Cover = Close < EMA( Close , 3 )
AND Open < EMA( Close , 3 );

SellPrice=ValueWhen( Sell, C, 1);
BuyPrice=ValueWhen( Buy,C, 1);
Long=Flip(Buy,Sell);
Shrt=Flip(Sell,Buy );


PlotShapes(shapeUpArrow*Buy,colorGreen, 0, L, Offset=-45);
PlotShapes(shapeDownArrow*Short,colorRed, 0, H, Offset=-45);
AlertIf( Buy, "SOUND C:\\Windows\\Media\\notify.wav", "Audio alert", 2 );
AlertIf( Sell, "SOUND C:\\Windows\\Media\\chord.wav", "Audio alert", 2 );
AlertIf( Cover, "SOUND C:\\Windows\\Media\\notify.wav", "Audio alert", 2 );
AlertIf( Short, "SOUND C:\\Windows\\Media\\chord.wav", "Audio alert", 2 );

_SECTION_END();

_SECTION_BEGIN("supp");
("Price");
RSIperiod = 15; // Param("RSI p",3,14,30,1);
Percent = 5; // Param("ZIG %",8,9,15,1);
EMAperiod = 5; //Param("EMA p",4,5,10,1);
HHVperiod = 8; //Param("HHV p",3,5,10,1);
NumLine = 2; //Param("Num Lines",3,1,20,1);

Base = DEMA(RSI(RSIperiod),EMAperiod);

GraphXSpace=0.5;
Plot(C,"",colorWhite,styleCandle);

for( i = 1; i <= numline; i++ )
{
ResBase = LastValue(Peak(Base,Percent,i));
SupBase = LastValue(Trough(Base,Percent,i));
Plot(ValueWhen( ResBase==Base, HHV(H,HHVperiod) ), "Resist Level", colorRed, styleLine);
Plot(ValueWhen( supbase==Base, LLV(L,HHVperiod) ), "Support Level", colorGreen, styleLine);
}

_SECTION_END();

_SECTION_BEGIN("SAR");
acc = Param("Acceleration", 0.02, 0, 1, 0.001 );
accm = Param("Max. acceleration", 0.2, 0, 1, 0.001 );
Plot( SAR( acc, accm ), _DEFAULT_NAME(), ParamColor( "Color", colorCycle ), ParamStyle("Style", styleDots | styleNoLine, maskDefault | styleDots | styleNoLine ) );

//=================TITLE============================ ================================================== ==================
_SECTION_BEGIN("Title");
if( Status("action") == actionIndicator )
(
Title = EncodeColor(colorWhite)+ ":EMA 3/15, Support & Resistance Levels using RSI:, SAR Dotted Line - buy/sell white arrow/triangle - short-cover orange arrow/triangle" + " - " + Name() + " - " + EncodeColor(colorRed)+ Interval(2) + EncodeColor(colorWhite) +
" - " + Date() +" - "+"\n" +EncodeColor(colorYellow) +"Op-"+O+" "+"Hi-"+H+" "+"Lo-"+L+" "+
"Cl-"+C+" "+ "Vol= "+ WriteVal(V)+"\n"+
EncodeColor(colorRed)+
WriteIf (Buy , " GO LONG / Reverse Signal at "+C+" ","")+
WriteIf (Sell , " EXIT LONG / Reverse Signal at "+C+" ","")+"\n"+EncodeColor(colorWhite)+
WriteIf(Sell , "Total Profit/Loss for the Last Trade Rs."+(C-BuyPrice)+"","")+
WriteIf(Buy , "Total Profit/Loss for the Last trade Rs."+(SellPrice-C)+"","")+
WriteIf(Long AND NOT Buy, "Trade : Long - Entry price Rs."+(BuyPrice),"")+
WriteIf(shrt AND NOT Sell, "Trade : Short - Entry price Rs."+(SellPrice),"")+"\n"+
WriteIf(Long AND NOT Buy, "Current Profit/Loss Rs."+(C-BuyPrice)+"","")+
WriteIf(shrt AND NOT Sell, "Current Profit/Loss Rs."+(SellPrice-C)+"",""));
AlertIf( Buy, "SOUND C:\\Windows\\Media\\Windows XP Startup.wav", "Audio alert", 2 );
AlertIf( Sell, "SOUND C:\\Windows\\Media\\Ringin.wav", "Audio alert", 2 );

_SECTION_END();

x = EMA(Close,3);
y = EMA(Close,15);

Buy = Close > EMA( Close , 15 )
AND Ref( Close , -1 ) > Ref( EMA( Close , 15 ) , -1 )
AND Cross(x,y);

buy arrow appear based on fulfillment of 3 conditions

1. candle should be above 15 days EMA
2. yesterday's close should be above yesterday's 15 EMA
3. EMA 3 crossover EMA 15

this afl is based on EMA not MA