Can any body explain what the hell this SPDF is ?(in simple language)

1.	Can any body explain what the hell this SPDF is ?(in simple language)
Answer» S= Sharp P= Principal D= Diffuse F= Fundamental S, p,d,f are the names of subshells within a shell whose values are determined by azimuthal quantum number. Their respective azimuthal quantum numbers are 0, 1, 2 and 3. These terminologies are adopted from Spectroscopic analysis of matters.<br>Subshells

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