what is "extent" in raster::stack?

Question

x <- raster::stack('D:/MODIS/MCD19A2.A2008355.h24v06.006.2018043191140.hdf')
band1 <- x[[1]]
band1
#class      : RasterLayer 
#band       : 1  (of  16  bands)
#dimensions : 1200, 1200, 1440000  (nrow, ncol, ncell)
#resolution : 926.6254, 926.6254  (x, y)
#extent     : 6671703, 7783654, 2223901, 3335852  (xmin, xmax, ymin, ymax)
#crs        : +proj=sinu +lon_0=0 +x_0=0 +y_0=0 +R=6371007.181 +units=m +no_defs 
#source     : MCD19A2.A2008355.h24v06.006.2018043191140.hdf 
#names      : Optical_Depth_047_1 

Does the extent means the MODIS data contained in hdf4 files?

Answer 1

"extent" refers to the spatial extent of the data. It shows the minimum and maximum x and y coordinates of the data.