This lag or lead means

if voltage has a value of 10 and current has 5 and lead or lag of 2 seconds then,

If at t=0 voltage is crossing point A(say)

then at t=(0+2) current will reach A

Provided the waveform is linear (magnitude constant)

other wise with time the magnitude will vary

If volt lead current ,volt will reach A fast

If volt lag current ,volt will reach A later

By reaching I mean Its situation in a wave, Where the waveform is a path for progressing

if voltage has a value of 10 and current has 5 and lead or lag of 2 seconds then,

If at t=0 voltage is crossing point A(say)

then at t=(0+2) current will reach A

Provided the waveform is linear (magnitude constant)

other wise with time the magnitude will vary

If volt lead current ,volt will reach A fast

If volt lag current ,volt will reach A later

By reaching I mean Its situation in a wave, Where the waveform is a path for progressing