Explain why some solar eclipses are total and some are annular.

Some solar are eclipse are total and some are annular because the eclipse are not a total circle so, at the different phase of year the moon and the sun are away from the earth at different degree.

Every occurring eclipse of sun are not considered as total solar eclipse. The moon are sometimes too small for covering the entire disk of the sun. And the annular eclipse are only happen when the moon covers the entire area of the sun.