Updating weights in Adaboost I'm studying the Adaboost algorithm. This algorithm updates the weight after training.  



This is the table when they explain about weight on Adaboost 




I'm confused about what this "weight" means. Is it:


weight for each node?
weight for each model? 
table weight column (more confusing)?
weight for each node?  $w_i$

weight for each model? $\alpha_i$

table weight column (more confusing)? The initial weight is set as $\frac{1}{M}$ where M is the number of data points. I assume the data2_1 is the update of data1_1 after being updated by a new weight for feature1 but it's a bit obscure due to lack of description about the title, etc. of the table.

weight for each node is being updated after a classifier is trained on the data and it's weight ($\alpha_i$) and the score is calculated. 

$T(x_i)$ is the final classifier but seemingly is lacks a sign before the expression. which is the sum of multiplication of each classifier with it's weight $\alpha_i$