override func numberOfSections(in tableView: UITableView) -> Int {
    // You need to return minimum one to show the cell inside the tableview
    return 1
}

override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    // return the number of rows inside the tableview.
    return 3
}


override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {

    let cell = tableView.dequeueReusableCell(withIdentifier: "Cell", for: indexPath) 
// identifier string should be same as what you have entered in the cell Attribute inspector -> identifier (see the image).

    // Configure the cell...
    cell.textLabel?.text = "Cell \(indexPath.row) :" + "Hello"
//cell have different style Custom, basic, right detail, left detail, subtitle.
//For custom you can use your own objects and constrains, for other styles all
//is ready just select according to your design. (see the image for changing the style) 

    return cell
}

override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
        // this delegate method will trigger when you click a cell
}

For custom tableview cell you need a class that is subclass from UITableViewCell, an example class you can see below.

class TableViewCell: UITableViewCell {

@IBOutlet weak var lblTitle: UILabel!

override func awakeFromNib() {
    super.awakeFromNib()
    // Initialization code
}

override func setSelected(_ selected: Bool, animated: Bool) {
    super.setSelected(selected, animated: animated)

    // Configure the view for the selected state
}

}

Your tableview delegates

override func numberOfSections(in tableView: UITableView) -> Int {
        // You need to return minimum one to show the cell inside the tableview
        return 1
    }

override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    // return the number of rows inside the tableview.
    return 3
}


override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    
    let cell = tableView.dequeueReusableCell(withIdentifier: "Cell", for: indexPath) as! TableViewCell
    // identifier string should be same as what you have entered in the cell Attribute inspector -> identifier.
    
    // Configure the cell...
    cell.lblTitle.text = "Cell \(indexPath.row) :" + "Hello"
    
    
    return cell
}

override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
    // this delegate method will trigger when you click a cell
}