This can be as a result of either your driving or the state of your vehicle.
Where your driving fell far below the normal standard so that you put, or would not be able to avoid putting, other people in danger as a result of your driving then you will normally be convicted. You can also be driving dangerously if the state of your vehicle is so dangerous that no sensible person would get on or into it.
What is the punishment?
Where convicted your licence must be endorsed and you must be disqualified for at least one year. More serious offences could receive a custodial sentence. You lose all of your licences and you will have to retake your tests before you get these back. Things are worse if you were caught driving dangerously having consumed alcohol or drugs, racing, showing off, carrying and/or disregarding warnings from passengers or driving dangerously for a long or deliberate period, as well as having previous convictions for bad driving or drink driving. Expect a prison sentence and extended ban of over 12 months and a compulsory retest.
Factors that would reduce the likely punishment are where there is a one-off piece of reckless driving, a momentary reckless error of judgment and where you have got a good driving record.
What are the alternatives?
Where you can persuade the court that your driving wasn’t actually dangerous the court can still convict on the lesser offence of driving without due care. The fine is lower, they may disqualify and you get less points on your licence. You are likely to need a solicitor in court to help convince them this is what should happen.