Let us write Newron's Universal Garvitational Law.
`F =G (m_1xxm_2)/r^2`
where `m_1,m_2 ` are mosses of the object and r is distance between them.
let mass of the one object `m_2=M_e` ,mass of the earth,and
`r=R_e` radius of the earth. The earth now attracts object with
mass `m_1` towards its centre by force `F=m_1g `
Thus acceration due to gavity depends on distance between centre of the earth and places.Since earth is not exctlt spherical ,so distances varies.So g will also varies from place to place.
Deep sea g more than 9.8
high Moutain g less than 9.8
some place on surface g=9.8