what is it when there is not a full powercut but a reduced voltage powercut?

Hello there hope I have got the right group - had a Powercut at 6.30am this morning, however although sockets nearly all went off I went into bathroom and the Fluorescent light fitting strip we have on at night was glowing but not at full brightness it was half or quarter of light and when i put the incandescent light above the mirror it lit but a dim golden glow.

All sockets seemed to be off except for the socket where my mobile phone was plugged in was still charging up my mobile phone and the socket where the wireless broadband router was plugged in was working and the lights were on the router. Now what I deducted from that was that we must of been getting some power most probably a quarter of 240volts and it wasnt a total power cut but why? why does it work like that in a storm and why was the electric not cut right off if say a overhead powerline came down in the storm?

- why would it be low power like that and not totally off? and can this long state like this ruin computers or tvs ect and other sensative electronic equipment because its not getting its full 240volts? after a while the electricity kept 'surging' on and off about 3 times to full power in half hour so in the end I killed the main switch on the fuse box because I didnt like all the buzzing noises and feared it would wreck me computer and stuff, again why in a power cut why does it have to surge on and off like that and not cleanly go off for a certain amount of time and then come on cleanly full power why blips and surges?

im pretty sure it cant be good for the electronics in the household?. - in the end the power was restored at 2pm in the afternoon which werent bad going. Let me say though I so admire the crews that have to go out in the stormy weather to get the power back on, it cant be easy and we was like without power from 6.30am to 2pm in the afternoon and it was still stormy and pouring with rain out there so they must have been having to battle this terrible weather to get the electrics back on. There was 90 houses out in our area this morning. So fair play to the crews for sorting it out quickly and in the lashing rain as well!